1. Field of Invention
The present invention relates generally to determining a concentration of glucose in interstitial fluid of a living animal using an optical sensor implanted in the living animal. Specifically, the present invention relates to purification of a raw signal including a glucose-modulated component to remove noise (e.g., offset and/or distortion) and converting the processed signal to a glucose concentration.
2. Discussion of the Background
A sensor may be implanted within a living animal (e.g., a human) used to measure the concentration of glucose in a medium (e.g., interstitial fluid (ISF) or blood) within the living animal. The sensor may include a light source (e.g., a light-emitting diode (LED) or other light emitting element), indicator molecules, and a photodetector (e.g., a photodiode, phototransistor, photoresistor or other photosensitive element). Examples of implantable sensors employing indicator molecules to measure the concentration of an analyte are described in U.S. Pat. Nos. 5,517,313 and 5,512,246, which are incorporated herein by reference in their entirety.
Broadly speaking, in the context of the field of the present invention, indicator molecules are molecules having one or more optical characteristics that is or are affected by the local presence of an analyte such as glucose. The indicator molecules may be fluorescent indicator molecules, and the fluorescence of the indicator molecules may be modulated, i.e., attenuated or enhanced, by the local presence of glucose.
The implantable sensor may be configured such that fluorescent light emitted by the indicator molecules impacts the photodetector, which generates a raw electrical signal based on the amount of light received thereby. The generated raw electrical signal may be indicative of the concentration of glucose in the medium surrounding the indicator molecules, but the raw signal may also include noise (e.g., offset and/or distortion) that affects the accuracy of the glucose concentration measurement produced from the raw signal.
There is presently a need in the art for a more accurate sensor capable of measuring glucose concentration in a medium of a living animal.